Differential screw micrometer



Feb 15, 1949. E. E. MODES. ,995 7 DIFFERENTIAL SCREW MICROMETER Filed June 21, 1946 70677/07? lC/wczra/j foa/eo,

ZZZ/M Patented Feb. 15 1949 UNITED STATES PATENT OFFICE DIFFERENTIAL SCREW MIQRGMETEB Edward E. Modes, Chicago, Ill.

Application June 21, 1946, Serial No.-.678,504

3 Claims.

This invention relates. to micrometer calipers and similar measuring instruments for accurately measuring dimensions, and more particularly to the provision of means in such instruments for directly and easily reading the measurement in tens of thousandths of an'inch.

Conventional micrometer calipers and the like, in use prior to my invention, reading to tens of thousandths of an inch, required the use of an additional pair of cooperating scales called a Vernier for reading the tens of thousandths of an inch, which is not direct in that mating of corresponding lines is required. Also in the conventional micrometers the graduations were placed directly on the barrel, as-a result of which the longitudinal movement of the thimble rela tively to the barrel fora given change in measuring distance is equal to that change.

In said prior micrometers, when reading an indication, the tenths digit is read directly as the number of major divisions visible on the barrel, but the hundredths and thousandths digits must he arrived at by a process of adding multiples and a fraction of .025, and the ten-thousandths digit must be read from the Vernier.

In the present invention I have overcome the above hazard of error, and labor of arriving at the final estimate of the measurement, by providing a multiplying sleeve which enables easily and quickly reading the correct measurement by merely counting the number of major divisions and subdivisions, no addition being involved and no Vernier being required for the last digit. In other words the measurement .4995" is easily read directly from the graduations visible on the main measurement reading portion of the instrument.

Among the objects of the present invention are: to provide a novel and improved micrometer instrument; to provide such an instrument in which the measurement is read directly; to eliminate in such instrument the need of a Vernier; to enable the correct reading of measurements by merely counting the divisions; to increase the number of graduations on the scale without interfering with the accuracy of the reading of the measured distance; and to provide an instrument of the type referred to that is easy and economical to manufacture and assemble, durable, efficient in operation, pleasing in appearance and positive and reliable in operation.

Other objects and advantages will become I panying drawing, wherein:

Fig. l is a side elevation of a micrometer caliper embodying my invention.

Fig. 2 is a-longitudinal central section through themicrometer of Fig. 1, partsbeing shown in elevation for convenience.

Fig. 3 is a transverse section on the line 3-3 of Fig. 2.

Fig. i is a. fragmentary side elevation of the scale showing a reading different than that of Fig. 1.

While my invention further resides in the combination, construction and arrangement of parts illustrated in the accompanying drawings, 1 have shown therein for illustrative purposes only, a preferred embodimentyand wish it understood that the same is susceptible of modification and change without departing from the spirit and scopeof the appended claims.

In the form shown in the drawing my invention is shown as'applied to a micrometer caliper comprising a U-shaped frame i having ananvil 2 which is providedwith an anvil measuring face 3. Frame l-eXtends-rearwardly into the barrel 4 which is formedwith alongitudinalbore 5 enlarged in'd-iameter at sand at an intermediate portion isformed with the internal threads 'l; Threadably mounted. to intereng-agewith threads 1 are similar threads't formed one spindle-9 so that the rotation of spindle 9 in one direction will cause it to move toward the anvil measuring face 3 and rotation in the oppositedirection will cause-it to recedetherefrom. Barrel it. at its rear end is formed with an enlarged bore it! of :a diameter tofreely receive the outermost edges of threads it formed upon the.elongated-sleevev i2 which is mounted upon the reduced diameter portion-i3 integrally iormed at the rear end of.

spindle S. The: reduced portion is atsits forward end is formed with a shoulderit against which abuts the forward end: oft sleeve i2.

Threads ii are of a greater lead than threads 8 for a reason more fully explained hereinafter. Mounted for longitudinal movement on barrel 4 is a multiplying sleeve it provided with abore It of a size to permitsaid longitudinalsliding movement on barrel l but oiclose enough fit to prevent undue v entry of dirt therebetween. Sleeve 55 is formediwith an elongated. groove i! which asshown i-n 3 is semicircular in cross section: Barrel-i-isiormed.adjacent its rear end witha depression or cavity 1 is which retains in rotatable captivity a spherical ball $9. This structure enables rotation of ball is in cavity l8 and at the same time facilitates longitudinal movement of sleeve I 5 longitudinallyof barrel 4.

3 To assist in reducing friction the cavity I8 is formed with nonspherical faces. Sleeve I is formed with a transverse wall at having a concentric opening which is formed with internal threads 2I of a pitch to interengage threads II, these threads as stated being of greater lead than threads 8. The sleeve I5 is elongated in order to provide sufiicient exposed outer surface for a scale as hereinafter more fully explained. Rotatably and longitudinally movable upon sleeve I5 is a thimble 22 which at its forward end overlaps sleeve I5 a substantial distance, said forward end being beveled at 23 to provide a thinner forward edge for more readily reading the graduations thereon as later explained.

As seen in Fig. 2 sleeve I2 is at its rear end formed with an enlargement 24 having an annular shoulder 25 against which abuts annular shoulder 25 formed on thimble 22. Rearwardly (to the right as viewed in Fig. 2) of shoulder 25 the enlargement 24 is formed with screw threads 21 upon which is threadably mounted a nut 26 which when tightened against the outer face of the shoulder 20 on the thimble will grip the thin ble and sleeve I2 for rotation together upon rotation of the thimble. end as viewed in Fig. 2) of the reduced portion I 3 of spindle 9 is threaded at 29 to receive nut 30, so that when this nut is gripped against the adjacent face of the enlargement 2 of sleeve I2,

rotation of this sleeve by thimble 22 will also rotate spindle 9. It is to be noted that when nut 28 is loosened, thimble 22 may be loosely rotated with relation to sleeves, and when nut 30 is loos The rear end (right hand 4 threads It be twice that of the lead of threads 8, Z am, for illustrative purposes only, assuming such difference in lead in the drawings. By making the lead or pitch of threads l I .020, the multiplying factor becomes .020 divided by .010 or 2. One turn of thimble 22 changes the measuring distance .010 between the end of spindle 9 and the anvil but the simultaneous relative distance of movement between the thimble and the sleeve is .020. This is because the thimble upon each revolution moves in one longitudinal direction .010 with relation to the barrel and at the same time the sleeve moves in the opposite direction .010 with relation to the barrel. This means that the relative distance of movement between ened the thimble 22 and sleeve I2 will be rotatable 91:.

with relation to the reduced portion 53 of spindle 9 for a purpose later more fully explained. In other words, loosening of nuts 28 and 30 will permit rotation of thimble 22, sleeve I2 and reduced portion I3 of spindle 9 withrelation to each other 1;-

for adjusting and setting purposes as later explained. When both of these nuts are tightened these parts will rotate togeher as a unit.

As stated above, threads I I are of greater lead than threads 8. By using a .010" pitch or lead for threads 8 it is possible to divide the-forward annular beveled edge of thimble 22 into ten major divisions, each equivalent to .001" change in measuring distance between the free end of spindle 9 and the measuring face 3 of the anvil 2. These 10 major divisions on the thimble 22 are indicated at 3| in Fig. 1. Each of these major divisions are subdivided into ten subdivisions 32, each equivalent to .0001" change in measuring distance without appreciably increasing the circumference of thimble 22 over that of the conventional size micrometer caliper. This means that both the thousandth digit and the ten-thousandth digit may be read directly upon the scale at the forward edge of thimble 22 without the use of a Vernier.

Formed upon the side of the sleeve I5 is a longitudinal scale 33 of graduations which will be longer in longitudinal distance than if the threads II were not of greater lead than the threads 8. As will be understood in Fig. 2, the threads i I being of greater lead than the threads 8, the sleeve I5 will move longitudinally along the surface of the barrel 4 toward the left (Fig, 2) when rotated in one direction at a greater rate thanif threads II were of the same lead as threads 8, it being understood that threads II and threads 8 rotate fixedly together upon rotation of thimble 22, when both nuts 28 and 30 are tightened in place. While it isnot essential that the lead of ment of the pindle 9.

the thimble and the sleeve is, in the present illustration twice that of the distance of movement between the end of the spindle and the anvil. This proportional movement may be changed by changing the difference in lead of threads I I with relation to the lead of threads 8 as desired. This gives a readily readable minimum subdivision on the sleeve I5 for the hundredths digit. The major divisions on the scale 33 of sleeve I5 give the tenth digits and each of these major divisions are divided into ten subdivisions which give the hundredths readings.

Nuts 28 and 30 are for adjustment purposes. When assembling the parts together, the spindle 9 is screwed into the barrel 4 until the measuring distance between the end of spindle 9 and anvil 3 is zero. meaning these points being just contacted. The multiplying sleeve I5 is next slipped longitudinally over barrel 4 with groove I! passing over the ball I9 which is rotatably seated in depression I8, and sleeve I2 is threaded into threads 2I in wall 20 of the multiplying sleeve I5. Thimble 22 is next slipped onto the enlarged portion 24 of sleeve I2 with the shoulders 25 and 2-5 in abutment and nuts 28 and 30 are then made tight. Nut 30 is then backed off slightly and sleeve I2 is then rotated in the sleeve I5 by rotation of thimble 22 until the zero mark on the multiplying sleeve I5 registers with the beveled edge of thimble Nut 30 is then tightened and nut 28 loos ened. Thimble 22 is then rotated with relation to sleeve I2 until the zero mark on the thimble registers with the longitudinal index line of scale 33 after which the nut 28 is tightened. The cooperating parts of the two scales now being in proper position and nuts 28 and 30 tightened, the readings may be then accurately read as the spindle moves rearwardly from its closed position and is adjusted in accordance with whatever measurement is being taken.

From the above description and the accompanying drawing it will be understood that the thimble and sleeve move in opposite directions and that the longitudinal movement of the multiplying sleeve I5 relative to the thimble 22 will be an increased amount because of the lead of threads I I being greater than the lead of threads 8. The fact that sleeve I5 is nonrotatable but longitudinally slidable with relation to the barrel means that for any lead of threads II greater than the lead of threads 8 the sleeve will move longitudinally in the opposite direction from that of the thimble and that the relative difference in movement between these parts will be greater than the move- This enables a greater number of graduations on the longitudinal measuring scale which makes possible a much more easy reading of the tenths and hundredths graduations and a direct reading on the front edge of 2. A micrometer measuring instrument as 15 1 001,471

claimed in claim 1, having means for preventing rotation of the multiplying sleeve with relation to the barrel and providin for longitudinal movement thereof as thespindle is rotated by the thimble.

3, A micrometer measuring instrument as 6 claimed in claim 1, in which the releasable locking means comprises a pair of nuts one of which threadably engages said threaded sleeve and the other of which threadably engages the end of the 5 spindle.

EDWARD E. MODES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 890,590 Anderson June 16, 1908 Spaulding Aug. 22, 1911 2,267,332 Hagstrom Dec. 23, 1941 FOREIGN PATENTS Number Country Date 5,080 Great Britain Dec. 17, 1900 8,798 Great Britain Oct. 2, 1906 

